Coated iron and steel articles and method of making the same



Patented Mar. 11, 1930 UNITED STATES PATENfD OFFICE mama JONES, OI DETROIT, MICHIGAN, SIG-NOB TO PARKER BUST-PBOOT' GOI- PANY, OI DETROIT, HICHIGAN', A. CORPORATION OF IIOHIGAI COATED IRON AND STEEL ARTICLES AND METHOD 0] BRING THE Io Drawing. Application filed June 18,

This invention relatesto coated iron and steel articles, and a method of producing the desired coatin on the articles.

More 'speci cally, the invention relates to iron or steel articles provided with a coating containing a com ound of silicon, and to a method of provi such a coating.

The coatin to which the invention relates may be relie upon to protect the surfaces to which it is app ied or it may be used as a foundation for another coating.

One-important advanta e of the invention is that the coating to whic it relates may be applied to pickled surfacesof iron or steel without intermediate preparatory operations other than washing. v

One specific method of providin iron or steel surfaces with a coatin forme in situ, and containing a com ound of silicon, willbe described with su cient detail to enable those skilled in the art to carry out the method, and thereafter some modifications of the described method will be discussed.

A dilute solution of phosphoric acid is formed, and a compound of silicon is introduced into this solution. The solution may be formed by dissolving in water acid phosphates of iron, manganese or zinc, or a combination of the acid hosphates of two or more of these metals, ormed as described in a co-pending application of applicant with Hobart H. Willard and Matthew Green, Ser. No. 83,736, filed Jan. 25, 1926, which eventuated into Patent No. 1,651,69 December 6, 1927', and preferred roportion is about twenty pounds of the p osphates to 125 gallons of water. The silicon compound may be ordinary sand.

This solution is boiled, and after four or five hours of boiling there is produced a whitish colloidal material which is apparently v silioio acid.

After the-appearance of the silicic acid, articles havin' surfaces of iron or steel are placed in the oiling solution, and a coating immediately begins to form on said surfaces. The exact chemical formulas of the ingredients of this coating have not been determined but the coating is known to comprise insoluble phosphates of the metals whose sol'-' 1H7. lei-kl 1T0. 198,696.

uble acid phosphates were introduced into the bath, and a silicon compound which is apparently a silicate of iron.

The silicic acid must be brought into contact with the surfaces to be coated in order to produce the silicon compound in the coating. The colloidal silicic acid is so nearly the specific 'ravity of water that it is readil distributed t roughout the bath b slight agitation. For a-sniall tank, merely ilm produces suflicientagitation to distribute t e silcic acid; but when boiling is not sufficient to bring the silicic acid into contact with the surfaces to be coated, other agitating means may be employed.

The coating readily forms on any clean surface'of iron or steel, including a pickled surface. It is preferable to wash the articles to'be coated after pickling, in order to avoid useless waste of chemicals in the coating bath, but other preparatory treatment of pickled surfaces is unnecessary.

If desired, the articles may be left in the bath for an houror so, or until the formation of coating ceases. Hydrogen is given off during the formation of the coating, so that the completion of the coatin operation is indipsted by the cessation o the hydrogen bub es. this limit, the resultant coating is sufficiently thick to provide an eflicient protection against rusting.

If an external coating of a diiferent nature is desired, the described coating may be used as a foundation, whether the operation is carried to its limit or is stopped far short of that limit. The coating is formed in situ and is integral with, or very intimately associated with, the coated article, and is very evenly distributed over the surface, so that it forms a very good foundation coating. As brief a periodas five minutes suflices to produce a coating sufficient to furnish a foundation for subsequent coating operations.

A well kn and steel surfaces has been to subject such surfaces to boiling in a dilute solution of phosphates of iron, man anese, zinc, etc. One difficulty encountere in carrying out this process is that articles cleaned by pickling If the coating operation is carried to.

own process of rust-proofing iron cannot be successfully rust-proofed by this method without intermediate treatment. With untreated pickled articles the bath containing phosphates of iron either does not attack the work at all, orproduces a coating having large crystals at separated intervals in.

a comparatively thin and inefiective coating. This produces what has been known in the trade as sparkle, recognized by the sparkling of the large crystals, and unsatisfactory m5 phosphates, the articles may be dipped for a short time in the bath first described, after havin been pickled and washed, and then trans erred to the usual rust-proofing tank. This preliminary treatment in the bath containing silicic acid results in a much quicker operation inthe regular rust-proofing tank, as well as eliminating the difiiculty described above as sparkle.

Difiiculty ,is encountered in providing pickled surfaces of iron or steel with other coatings, such as enamel or p oxylin finish or ordinary paint, for examp e, without intermediate treatment of the surfaces after pickling. A preparatory coatin formed in the bath of di utephos horic acid containing colloidal silicic acid orms a good founda-- tion for such other coatin as well as for further coating with phosp ates.

Ordinary sand is referred to above, but

other materials containing silica may be used to produce the necessary silicic acid. The re 'minary boilingl necessary to bring the ath to proper con 'tion for coating may be shortened by the use of fused silica, or SILllCBr in other forms that are more readily attacked by the acid in the solution.

One way in which the bath containing phosphates may be formed has been described, but it will be readily understood that a similar bath may be formed in other ways. The silicic acid may be produced in other ways either in the bath or separately and introduced into the bath; and the dilute solu- 'tion of phosphoric acid and phosphates may be produced in any of the known ways for producing such a rust-proofing solution.

- However, after the bath is once formed, the

introduction of sand into the bath to maintain the supply of silicic acid is simple and effective, as sufiicient silicic-acidis formed during the regular coating rocess to maintain a supply, and nothing urther than the presence of the sand in the bath during the coating operation is necessary to maintain ance with the disc osure of the patent identified above.

Where a dilute solution of hosphoric acid is referred to in the appende claims, it will be understood that a solution is referred to which is suitable for coating surfaces of iron or steel with insoluble phosphates.

Having described the nature of my invention and a method of carrying it out, what I claim is:

1. Iron or steel articles, or articles having surfaces of iron or steel, having a coating formed in situ on said surfaces and comprising a silicate of iron and a phosphate.

2. Iron or steel articles, or articles having surfaces of iron or steel, having a coating formed in situ on said surfaces and comprising insoluble phosphates of metals and a compound of silicon.

3. The method of coatin an article having a surface of iron or stee roughened as by pickling, which comprises bringin into contact with said surface a collolda material capable of reacting with phosphates to form an insoluble material, and subjecting said material to the action of phosphates while in contact with said surface.

4. The method of providin an article having a surface of iron or stee with a coating which consists in boiling said article in a dilute solution of phosphoric acid containing colloidal silicic acid.

5. The method of coating pickled surfaces of iron or steel, which consists in boiling articles having such surfaces in a dilute solution of phosphoric acid containing colloidal silicic acid.

6. The method of coating articles having surfaces of iron or steel, which consists in formin a dilute solution of phosphoric acid containing a compound of silicon, boiling the solution until col oidal silicic acid is formed, and thereafter subjecting said surfaces to the action of the boiling solution.

7 A method of preparing for coating articles having surfaces of iron or steel, which consists in pickling said surfaces, thereafter washing the surfaces and applying to the surfaces 0. boilin dilute solution of phosphoric acid contaming colloidal silicic acid for a sufficient time to cm a. foundation film over said surfaces.

8. A bath for coating articles having surfaces of iron or steel roughened as by pickling, comprising a dilute solution contaming phosphoric acid radical and a colloidal material capable of reacting with said radical to form an insoluble product. v

9. A bath for coating articles having surfaces of iron or steel, comprising a dilute 

